St Tropez is one % only and I know that a lot of geeks are fans of ST, I am not one of them. My reasons for this are that I work for a salon whose spray tan choice is St Tropez and they tend to book as many spray tans as they can with me as they know I am experienced.
The guide colour in my opinion is a little green looking and the developed colour can be a little "tangoey".
There are plenty of great spray tan solutions on the market other than St Tropez, get some other recommendations or if you are asking because you want to start up a spray tan business then get some samples for yourself, try them and make up your own mind.